cc: Phil Jones , Gavin Schmidt date: Wed, 30 Sep 2009 12:41:44 -0400 from: Michael Mann subject: Re: attacks against Keith to: Tim Osborn Tim, Phil, thanks for the clarification on this. the points are well taken. I'm fairly certain MBH98 and Mann et al PNAS are entirely independent of this particular (Briffa et al RCS version) of the Urals/Yamal data, at least Malcolm believes that to be the case. It sounds as if Mann and Jones is not. Meanwhile, Darrell Kaufman is re-rerunning their analysis w/out Yamal to establish the result isn't sensitive to it (he's pretty confident its the case). I don't know about the Hegerl/Crowley/Juckes et al analyses--do you know which of any used this series, but interested if you have any insights into that yourself. we're trying to get a tally on the number of studies that are completely independent of this particular series, or have been shown to give largely similar conclusions w/out it (I think that is true for Osborn and Briffa still, is it not?) There are at least three issues we need to deal with here, 1) is the specific criticism of Keith's particular rendition of the Yamal series legitimate (probably not--we hope this can be established), 2) Which of the existing hemispheric reconstructions are specifically affected (we know that many are not), 3) does this undermine the broader conclusions of e.g. the IPCC on the key issue, i.e. anomalous nature of recent hemispheric warmth (no, because many of the estimates are entirely independent of this series; the Mann et al PNAS result was even shown to be independent of using tree-ring data at all). thanks for your continued help w/ this, miike On Sep 30, 2009, at 12:15 PM, Tim Osborn wrote: At 16:06 30/09/2009, Michael Mann wrote: And Osborn and Briffa '06 is also immune to this issue, as it eliminated any combination of up to 3 of the proxies and showed the result was essentially the same (fair to say this Tim?). Mike, yes, you're right: figs S4-S6 in our supplementary information do indeed show results leaving out individual, groups of two, and groups of three proxies, respectively. It's attached. I wouldn't say we were immune to the issue -- results are similar for these leave 1, 2 or 3 out cases, but they certainly are not as strong as the case with all 14 proxies. Certainly in figure S6, there are some cases with 3 omitted (i.e. some sets of 11) where modern results are comparable with intermittent periods between 800 and 1100. Plus there is the additional uncertainty, discussed on the final page of the supplementary information, associated with linking the proxy records to real temperatures (remember we have no formal calibration, we're just counting proxies -- I'm still amazed that Science agreed to publish something where the main analysis only involves counting from 1 to 14! :-)). But this is fine, since the IPCC AR4 and other assessments are not saying the evidence is 100% conclusive (or even 90% conclusive) but just "likely" that modern is warmer than MWP. So, yes, it should be possible to find some subsets of data where MWP and Modern are comparable and similarly for some seasons and regions. And as you've pointed out before, if any season/region is comparable (or even has MWP>Modern) then it will probably be the northern high latitudes in summer time (I think you published on this, suggesting that combination of orbital forcing, land-use change and sulphate aerosols could cause this for that season/region, is that right?). So, this Yamal thing doesn't damage Osborn & Briffa (2006), but important to note that O&B (2006) and others support the "likely" statement rather than being conclusive. Cheers Tim Dr Timothy J Osborn, Academic Fellow Climatic Research Unit School of Environmental Sciences University of East Anglia Norwich NR4 7TJ, UK e-mail: [1]t.osborn@uea.ac.uk phone: +44 1603 592089 fax: +44 1603 507784 web: [2]http://www.cru.uea.ac.uk/~timo/ sunclock: [3]http://www.cru.uea.ac.uk/~timo/sunclock.htm -- Michael E. Mann Professor Director, Earth System Science Center (ESSC) Department of Meteorology Phone: (814) 863-4075 503 Walker Building FAX: (814) 865-3663 The Pennsylvania State University email: [4]mann@psu.edu University Park, PA 16802-5013 website: [5]http://www.meteo.psu.edu/~mann/Mann/index.html "Dire Predictions" book site: [6]http://www.essc.psu.edu/essc_web/news/DirePredictions/index.html